Polymeric thin film electro-optical (EO) modulator devices based on guest nonlinear optical (NLO) chromophores dispersed in a polymeric material are known. The devices function because the NLO chromophores exhibit a high molecular hyperpolarizabity, which when aligned into an acentric dipolar lattice by an applied poling field, increases the EO activity. The performance of such devices is limited or diminished by the randomizing of the acentric order originally imposed on the lattice due to physical events within the polymeric material. These events include polymer creep, polymer glassy behavior above glass transition state, and chromophore/polymer phase segregation and aggregation.
One approach to surmount these problems includes using a polymeric material exhibiting a relatively high glass transition state well above the operating temperature of the device. However, this strategy has been limited because the NLO chromophore has been found to exert a plasticizing effect on the polymeric material, thereby lowering the glass transition temperature of the composite material relative the undoped polymer.
A second approach employs crosslinking the polymeric material to “fix” the orientation of the poled chromophores. Difficulty in controlling the reaction conditions during device fabrication has limited this approach. To be a viable approach, the crosslinking must not occur before poling is complete. Poling is generally conducted at temperatures at or about the glass transition temperature of the polymeric material. Therefore, the crosslinking needs to occur “on demand”.
There remains a continuing need for still further improvements in the polymeric materials used to maintain the oriented NLO chromophore lattice.